It is widely recognized that the use of a simple loopback (LB) function provides necessary OAM capability for fault location, continuity verification, as well as round trip delay (RTD) measurements. It was agreed in the ITU study group to include this function for the future enhancement of frame relay service (FRS) in draft Recommendation I.620. However, the previously proposed LB mechanism in I.620 was analogous to that selected specifically for ATM networks and is not suitable for frame relay (FR) requirements in terms of complexity and overhead.
The OAM LB function for FR needs to be simple and introduce minimum additional processing and bandwidth overhead. However, it should also be flexible to enable additional functionality to be incorporated as required for specific OAM applications. The present invention solves these problems by simplifying the LB OAM procedure, is more efficient than the existing procedure and should be more suitable for the enhancement of future FRS.